Access to antiretroviral therapy (ART) is becoming available to children in India for the first time through an initiative from the National AIDS Control Organization (NACO). The mandate for treating HIV infected children <15 years of age will be followed in major centers, including the Tuberculosis Research Institute (PI, Dr S Swaminathan) which is a major pediatric HIV center in South India. This project, between a US pediatric immunologist (S. Pahwa) and the Indian PI proposes to provide insights into HIV disease pathogenesis that have implications for future management of HIV infected subjects world wide. These studies will also lay the groundwork for subsequent challenging and innovative treatment protocols, clinical trials and future vaccine studies. Our specific aims are centered around the following hypotheses: 1. The nadir of NaTve CD4 T cells prior to starting ART predicts capacity for CD4 T Cell reconstitution; 2. Loss of CD127+ CDS T Cells or expansion of CD127-CD8 T Cells is associated with aberrant immune activation and disease progression, 3. Reconstitution of Dendritic Cell function is essential for functional immune reconstitution. These studies will apply novel and most current immunologic evaluations by flow cytometry and real time PCR in assays that require minimal blood volumes to characterize immunological status of HIV infected children, including those who initiate treatment with ART and those who have not progressed to reach eligibility standards for antiretroviral treatment. All new immunologic assays will be performed prospectively and the results analyzed in the context of current established indicators of disease progression, i.e. CD4 counts and virus load. The proposed investigations will provide insights into HIV disease pathogenesis that have implications for future management of HIV infected subjects world wide. These studies will also lay the groundwork for subsequent challenging and innovative treatment protocols, and future vaccine studies. [unreadable] [unreadable] [unreadable] [unreadable]